Fuses for projectiles



June 1956 G. KUHN 2,750,889

FUSES FOR PROJECTILES Filed Feb. 14, 1951 2 Sheets-Sheet 2 "finite States Patent FUSESFOR PROJECTILES Georges Kuhn, Geneva, Switzerland, 'a's'signor to Melina 'S. A., Binningen, Switzerland, 'a corporation of Switzerland Application February 14, 1951,'Serial No. 210,861

Claims priority, application Switzerland lMayZll, .1950

1 Claim. (Cl. 102-79) This invention relates .to fuses of the instantaneous or direct action type for projectiles having rotary motion about their axes during projection from a gun and during flight, and more particularly has reference to such fuses provided with a firing pin and a safety device including one or more locking members for securing the firing pin in inactive position.

Heretofore such fuses have been provided with safety devices of three different main types as follows:

1. The type with an axial slug or inertia .mass secured by a leaf spring and which can release the safety device only after the axial acceleration imparted to the projectile has ceased.

2. The rotor type secured by the firing pin or by apin in the form of a cylinder with its axis at right angles to that of the fuse, which cylinder-or rotor begins to oscillate upon firing, and comes to a stable position permitting detonation only after several oscillations, that is to say, after the projectile carrying the fuse has left the muzzle of thegun.

3. The liquid type based on the how of a liquid through a diaphragm or a hole of very small diameter, comprising a plate secured by a spring, and :a membrane, which plate holds on one side of the center of the fuse a liquid of high density and on the opposite side, a mass of lead which can shift the plate and allow free passage of .the firing .p'm only after the liquid, having slowly flowed through a small orifice, shifts the center of gravity of the plate towards the side with the lead mass.

When a device of the first type is "used in projectiles for firing from automatic arms in which the movements of the breech are produced by means of gases withdrawn from the muzzle of the gun itself; it is not possible to guarantee normal operation of the safety device because in such arms the taking of gas from the side or the muzzle produces irregularities in the axial acceleration to which the projectile is subjected, which irregularities may cause premature arming of the fuse.

In the second type of device indicated above, since the rotor or cylinder during each oscillation passes through a mid-position in which arming of the fuse can occur, there is no real trajectory security whatever since if the projectile should encounter an obstacle while the rotor is in such a position, detonation of the charge could take place.

The third type of safety device mentioned above theoretically ensures a good trajectory safety. However, as the liquid used in the device is usually mercury which attacks certain metal parts of the fuse, the trajectory safety is not assured after a certain duration of storage. Also, the manufacture of such safety devices is intricate in view of the manipulation of mercury.

An object of this invention is to provide a muzzle safety device which avoids the disadvantages of the prior art.

Another object of this invention is to provide a muzzle ice safety device for 'a projectile fuse comprising a firing pin having a flange or "boss, a hollow member or cage surrounding the boss or flange on the firing pin and having loeking'members positionedbetween the boss or flange and the bottom 'ofthe cage to retain the firing pin in inoperative position, the circumferential wall of the cage having a slot provided therein for the egress of the locking members, a stop on the inner surface of said wall at the one side of the slot and the inner surface of said wall being of ramp formation sloping radially outwardly from the .stop to the slot in spiral form, and means releasable .under the action of centrifugal force covering said slot, said ramp, slot and stop being so positioned and constructed that upon firing the projectile from 'a gun the angular accelerationimparted to the fuse and the inertia of the locking members will retain them in the cage against the stop, but on termination of the acceleration, centrifugal force acting on the locking members will move them along the ramp to and through the slot out of the path of movement of the flange carried by the firing 12in.

A better understanding of the present invention can be had by referring to the annexed drawings in which:

Figure 1 is an axial sectional view of a projectile fuse embodying the features of the present invention,

.Fig. 2 is a sectional viewtak'en on 'line IIH of Fig. l with 'the'locking members in safety position,

Fig. '3 is a view similar to Fig. '2 showing the locking members .in armed position of the fuse.

As shown in the drawings, a projectile fuse according to the present invention comprises a body 1 having a firing pin .2 mounted therein for axial movement and provided with a point for engaging a primer or detonating cap 17. Aboss or flange 3 is carried by the firing pin and is engaged by one end of a slide or sleeve 4 surrounding the firing pin 2 and pressed against the same by a spring 5 surrounding the pin '2 and received in an axial bore of the .slide 4. The other end of spring 5 is received in a seat 6 of the body 1. The sliding member 4 has radial bores '7 in which are arranged plungers 8 with rounded ends cooperating with a conical surface 9 on a socket .10 under the action of centrifugal force.

Socket I0 is fixed in the body 1 of the fuse .and serves as a guide for the axial movement of the slide or sleeve 4.

Between the soke't .10 and the primer 17 is positioned a hollow member or cage 11 having a bottom provided with an opening 1'2 for the passage of the end of the firing .pin .2, and a circumferential wall 13 provided with a slot or opening 14 and an inwardly projecting stop 15 ad- ,jacent the slot 14. As clearly shown in Figs. 2 and 3.,ithe inner surface of wall 13 is in the 'form of a spiral ramp increasing in radius from the stop 15 to the opening 14.

Within the cavity or hollow space surrounded by the wall 13 is positioned the boss or flange 3 of the firing pin. Between the flange 3 and the bottom of the cage 11 are positioned a plurality of balls 16 which serve to space the flange 3 from the bottom of cage 11 and to prevent the firing pin 2 engaging the primer 17 under the action of spring 5.

Body 1 is provided with an annular recess 18 about the cage 11 to receive the balls 16 when discharged from the cage through the opening or slot 14. Before the projectile equipped with the fuse is fired from a gun, the balls 16 are retained in the cage by an annular spring 19 sur rounding the wall 13 and closing the opening or slot 14. Also, the flange 3 pressed against the balls 16 by spring 5 serves to retain the balls in position as shown in Figs. 1 and 2.

The operation of the mechanism is as follows:

On firing the gun, the fuse is subjected, while the projectile is in the barrel of the gun, to the effects of axial and angular accelerations and rotates at high speed about its axis in the direction of the arrow 20, Figs. 2 and 3, and the balls 16 are held within the cage or guide by their own inertia, the last ball bearing against the stop 15. The slope of the spiral ramp on the inner surface of wall 13 is made such that the force of inertia of the balls is greater than the component of centrifugal force tending to expel them through the opening 14. The inertia of the balls thus holds them in place until the projectile leaves the barrel of the gun. Meanwhile, the spring 19 has expanded under the action of centrifugal force and is forced against the wall of the annular recess 18, as shown in Fig. 3.

Also, under the action of centrifugal force, the plungers 8, Fig. l, in contact with the conical surface 9, efiect an axial displacement of the slide member 4 which cornpresses the spring 5 and'at the same time unloads the boss 3 of the firing pin 2. Consequently, since angular acceleration of the projectile has now ceased, the balls 16 are subjected only to centrifugal force and can follow the spiral path of the ramp-like inner surface of the wall 13 of the cage 11 to discharge one by one through the opening 14 and enter'the recess 18, as shown in Fig. 3. i The fuse is now armed, that is, the firing pin 2 is free to come into contact with the primer or percussion cap 17 either upon impact of the projectile, or due to operation of the self-destruction device.

The curvature of the inner surface of the Walls 13 of the cage 11 forming for the balls 16 a guide of generally spiral shape, is so designed as to effect discharge of all the balls 16 upon cessation of angular acceleration of the projectile. Since the balls cannot leave their cage 11 before this acceleration has ceased, perfect muzzle safety is obtained with this device.

Instead of a single cage with a spiral guide, the fuse may comprise a plurality of such cages, each containing one or more balls.

In another modification, the ramp formed by the inner surface of the wall 13 instead of having a generally spiral form, may have on at least a part of its length, the general path of a spiral helix developing in the direction of the point of the projectile and so arranged relatively to the fuse axis that in a plane at right angles thereto, the said ramp will retain a generally spiral form. Thus, while the projectile is traversing the barrel of the gun, the balls 16 are held in the cage 11 not only by the effect of the angular acceleration to which the projectile is subjected, but also by the effect of the axial acceleration. As these two accelerations are exerted as long as the projectile is moving inside the barrel, the balls 16 cannot come out of the cage 11 until the projectile has left the barrel.

The safety device described is specially advantageous for small caliber projectiles, but may be used in projectiles of all calibers, with or without a self-destruction device.

I claim:

A direct action fuse for a projectile having rotary motion about its axis during projection from a gun and during flight comprising a body, a primer fixedly positioned therein, an axially movable firing pin provided with a boss mounted for movement towards the primer and a muzzle safety device for blocking movement of the firing pin toward the primer, said safety device comprising a fixed cage concentrically mounted about the firing pin and having a circumferential wall provided with a slot. therein, the inner surface of said wall being in the form of a spiral ramp extending through an arc of less than 360 and increasing in radius in the direction of rotation of the projectile, an annular recess in said body defined by an inner surface of said body and the outer surface of said wall concentrically disposed radially outward of the boss, said recess being in communication with said ramp through said slot, a stationary stop integralwith said wall projecting into the cage at the trailing edge of said wall where the spiral ramp is of smallest radius, said stop forming one .wall of the slot and the leading end of the ramp forming the other wall of the slot, said slot being of a size to complete an arc of 360 with the ramp, a number of balls being provided to fill said cage and being positioned about the pin and serving to engage the boss on the pin to prevent movement of the pin toward the primer, the slope of said ramp being such that when the fuse is subjected to acceleration while traveling through a gun barrel, the inertia of the balls will cause them to bear against the stop, the inertia of the firing pin causing the balls to be held in that position, said balls being pressed between the bottom of the fixed cage and the boss of the firing pin, but when acceleration ceases, the pressure of the boss on the balls will cease, releasing the balls, and centrifugal force acting on the balls will cause them to move along said ramp away from said stop toward the slot and leave the cage successively through the slot thereby freeing the firing pin, and an annular leaf spring releasable under the action of centrifugal force embracing the outer wall of the cage and closing said slot for retaining the balls in the cage and preventing their removal through the slot prior to firing the projectile from a gun.

References Cited in the file of this patent FOREIGN PATENTS 174,757 Germany Sept. 10, 1906 174,829 Germany Sept. 10, 1906 77,566 Austria Aug. 11, 1919 

